1. Field of the Invention
The present invention relates to surge protection for amplifiers.
2. Background Art
An amplifier is a device used for increasing the power and/or amplitude of a signal. Different types of amplifiers exist, with each amplifier type defined as an amplifier “class.” Example amplifier classes include class A, which is a more linear, less complex, and less power efficient class of amplifier, and classes A/B, B, C, D, etc., which are less linear and more complex than class A amplifiers, but are more power efficient. Such amplifiers may be used many types of applications.
Line drivers, power amplifiers and further amplifier circuits often drive very high power signals onto very low ohmic loads, such as antennas, phone lines, cables, and other such media. Due to the high power nature of these circuits, amplifier classes other than class A (e.g., class A/B, B, C, D, etc.) may be desirable to achieve high power efficiency. For class A differential amplifiers, the maximum load current is limited by a fixed current source. For higher class amplifiers, output current values are governed by the resistive load and the signal amplitude level.
In many wired applications, the signal lines driven by these amplifiers can be disconnected or connected at will by a user or technician independent of whether the amplifier is transmitting. As a result, a potential exists that the signal line will be accidentally shorted, causing a momentary surge in current. This shorting may cause permanent damage to the amplifier integrated circuit chip due to a resulting large power dissipation by the amplifier, or device breakdown. Even in line driver applications, where many implementations utilize line impedance back-match resistors, an accidental short may still result in dissipation of twice the line power, and may potentially damage the amplifier integrated circuit chip. Thus, ways for avoiding damage to amplifiers due to such shorting are desired.